Cylindrical Heat Research Articles

Study of natural convection heat transfer for a cylindrical and semicylindrical heat transfer system geometry

The paper presents the experimental and numerical study of the heat transfer parameters for the heated tube bank and arc-shaped plate made up of four tubes and four arc protrusions arranged one above the other. To evaluate the local heat transfer coefficients, the holographic interferometry is used as the experimental method, while the numerical simulations are performed by the Ansys Fluent software. The tube bank supplemented by the fin of different thickness and the double arc-shaped plate is further considered to improve the heat transfer parameters and the numerical results are compared with the basic arrangements. Considering the natural convection, the Rayleigh numbers are specified in the range of 16,460 to 46,340. It is observed that the tube bank achieves a higher average Nusselt number in the range of 37%–82% compared with the other arrangements depending on the Rayleigh number. The tube bank with fins does not increase the heat transfer parameters; however, there is an increase in average heat flux compared to the tube bank without fins. The double arc-shaped plate arrangement slightly increases the heat transfer and markedly increases the average heat flux compared to the single one. The highest average heat flux is achieved for the double arc-shaped plate and tube bank with fins in the range of 27.430 Wm-2 to 126.139 Wm-2.

Analysis of thermal performance a heat pipe for concentrated photovoltaic cooling

Heat pipes are used in this study for the concentrated photovoltaic (CPV) passive cooling. Investigations have been done in two steps: in the first step, the heat pipe's thermal performance in the horizontal position has been tested. Two sets cylindrical heat pipes with identical diameters (6 mm) but of different lengths (250 mm and 150 mm, respectively) were employed. Each set consists of three heat pipes. The results of the study showed that the heat pipe has a maximum operating point that is dependent on both the intensity of the incident light and the surrounding temperature. Moreover, this operating point could be determined. For high light intensity, a long heat pipe performs better than a short one, and vise versa. In the second step, a heat pipe passive cooled CPV system has been investigated for both long and short heat pipe systems. The performance of heat pipe cooled CPV system was compared to that of the traditional fins-cooled CPV system. Results showed that at light concentrations of 55 X, cooling a solar cell with a heat pipe enhances its maximum output power by 6% for a long heat pipe and by 7% for a short heat pipe, respectively. While at 210 X illumination concentration, long and short heat pipes, respectively, produced gains of 16 and 12% in the cell's maximum output power.

Traveling Wave Cylindrical Induction Heating System

The paper deals with the traveling wave cylindrical heating systems. The analysis presented is analytical and a multi-layer model using cylindrical geometry is used to obtain the theoretical results. To validate the theoretical results, a practical model is constructed, tested and the results are compared with the theoretical ones. Comparison showed that the adopted analytical method is efficient in describing the performance of such induction heating systems.

Micro-grooved circular miniature heat pipe for thermal management: Experimental and analytical investigations

In this paper, thermal performance of a cylindrical micro-grooved heat pipe is experimentally and mathematically investigated. The experimental tests are conducted included the optimum working fluid filling ratio, heat pipe inclination, and input heat load. The new correlations of micro-grooved heat pipe condensation and evaporation heat transfer coefficients are proposed basing on the experimental data. A coupled thermal and hydraulic model is developed to predict the heat pipe local thermal resistances and operating temperature regarding the effect of the architectural size. The Experimental results show that the heat pipe thermal performance is not affected by the inclination angle. Whereas the heat pipe performance is better at horizontal position. It showed that the micro-grooved heat pipe could provide an efficient performance even if the condenser is longer that 40% of the total length and the heat pipe microgrooves aspect ratio higher than 37%.

A new laser welding method of two transparent plastic parts based on reflector assisted method

It is a challenging work to joint two transparent plastic parts using traditional laser welding because the absorptivity of transparent plastic on short wavelength (800–1000 nm) laser energy is very low. During the laser welding of two transparent plastic parts, although laser absorber and long wavelength (1600–2000 nm) laser can obtain the high-strength weld joint, the problems of unattractive weld joint or pollution will occur when laser absorber is used, and the laser energy utilization coefficient is about 70% when long wavelength laser energy is used. To address this issue, this paper proposes a new production method for the absorber-free laser welding of two transparent plastic parts based on reflector assisted method. From three-dimensional thermal model, it can be found that the simulation data of the modified Gauss cylindrical body heat source show better agreement with the experimental result than those of Gauss surface heat source and Rotary-Gauss body heat source. In addition, for the same the weld joint width on the contact surface, the reflector assisted laser welding method can decrease the laser energy consumption by about 20%. Moreover, the maximum shear force of weld joint can be up to 1315 N. Under the same process parameters, the reflector assisted method can increase the shear strength of weld joint by 15.3%. Hence, the reflector assisted method has good application and promotion value in laser welding two transparent plastic parts.

Code Benchmark of the HTTF Pressurized Conduction Cooldown Test Using SAM

The High Temperature Test Facility (HTTF) at Oregon State University is an integral system test facility to simulate postulated reactor transients of prismatic high-temperature gas-cooled reactors(HTGRs). A series of test campaigns was launched, providing abundant test data that could be used to benchmark reactor system analysis codes like the System Analysis Module (SAM). In this study, a SAM model of the facility is developed based on the two-dimensional (2D) ring model approach. All components including the ceramic matrix, graphite heaters, helium coolant channels, core barrel, upcomer, pressure vessel, and reactor cavity cooling system are modeled as concentric cylindrical rings. The model is used to simulate one of the benchmark problems—Pressurized Conduction Cooldown (PCC)—within the scope of the Organisation for Economic Co-operation and Development Nuclear Energy Agency International HTTF Benchmark. The simulations consist of two parts. In the first part, operating and boundary conditions as well as thermophysical properties of materials are specified for the benchmark problem. Results from the first part will be used in code-to-code comparison. In the second part, the SAM model is used to simulate Test PG-27, which is the first PCC test carried out in the HTTF, with only two of the ten heater banks activated. The results in the second part are used for code-to-data comparison. Because the helium coolant flow rate is not measured in this facility, it is estimated using the input power and inlet/outlet coolant temperatures. Additionally, radial heat flow in the ceramic blocks is complicated by hundreds of cylindrical coolant channels and heater rods embedded in them. As such, it is necessary to deduce an effective thermal conductivity for the ceramic to analyze the core thermal behavior. SAM predictions of the helium coolant and ceramic temperatures are compared with test data measured in three equivalent sectors. Overall, the SAM results agree reasonably well with test data within the variation of data among the three sectors, which demonstrates SAM’s capability in capturing transient effects in HTGR using the simplified 2D ring model.

A comprehensive investigation of PCM based annular thermoelectric generator for energy recovery: Energy conversion characteristics and performance evaluation

Annular thermoelectric generators (ATEG) are increasingly attracting attention and are pivotal in thermal energy recovery due to their unique characteristics, which can be perfectly adapted to cylindrical heat sources. Considering the efficient thermal management and power generation of thermoelectric generator (TEG), phase change material (PCM) can be integrated with the cold side of TEG as a favourable cooling medium to meet its functional requirements. However, previous studies have focused on the intrinsic connection between flat-plat TEG and PCM, while the impact of PCM on ATEG has not been systematically explored. In the present study, an annular thermoelectric generator with PCM (ATEG-PCM) under a pulsed heat source is proposed, and its dynamic characteristics and energy distribution are evaluated. The effects of PCM parameters such as height, latent heat and melting temperature are comprehensively explored from multi-index, including PCM temperature, liquid fraction, temperature difference, output power, energy and exergy efficiencies. Furthermore, a comparative investigation of ATEG-PCM, PCM-ATEG where PCM is applied on the hot side, and ATEG without PCM is further carried out to clarify the coupled mechanism of PCM on thermal management and power generation enhancement of ATEG. The results indicate that the energy efficiency of ATEG-PCM has saturated at PCM height of 10 mm to 12 mm, while the exergy efficiency merely slightly increases. Especially, the PCM melting temperature merely affects the time at which PCM initiates to change from solid state to liquid state, without affecting the total energy efficiency of ATEG-PCM. Furthermore, the comparison analysis determines that ATEG-PCM deserves more attention, judging by thermal management and power generation. This work not only contributes to the understanding of the coupling mechanisms between PCM and ATEG but also provides a research direction for energy recovery in PCM based ATEG hybrid system.

Numerical Simulation of Heat Transfer within a Cross Section of a Cylindrical Heat Pipe

The presented work concerned a computation of two-dimensional heat transfer by laminar natural convection in a heat pipe cross section. The cylindrical annular space was categorized into two cases, in the first case the space was filled with a Newtonian fluid and the second case filled with a fluid-saturated porous medium. The mathematical model was described by continuity, momentum and energy equations in the cylindrical coordinates system using Boussinesq’s approximation and Brinkman’s equation. The numerical simulation was carried out using Comsol Multiphysics software. The effects of Rayleigh number, aspect ratio and permeability on the temperature and the velocity fields were examined and results obtained were validated and found to be qualitatively in a good agreement with those in the literature.

Detecting pipeline leakage using active distributed temperature Sensing: Theoretical modeling and experimental verification

This paper presents a feasibility study on leak detection of buried pipelines using the active distributed temperature sensing (ADTS) method. The proposed solution involves the use of actively heated fiber optic (AHFO) cables arranged parallel to the pipelines, allowing for changes in the thermal properties of the surrounding soil to be captured and correlated with leakage accidents. This problem was modeled as an infinite cylindrical or linear heat source buried in porous media with seepage flowing inside. AHFO sensors were designed to verify the proposed method through scale-reduced model tests. The fiber optic temperature sensing technology based on optical frequency domain reflectometry (OFDR) was used to continuously monitor temperature profiles. The test results demonstrate that the ADTS solution has greatly improved the accuracy of passive temperature sensing methods. The feasibility of the solution was evaluated regarding different levels of leakage estimation, namely, identification, location, and quantification. This paper presents the first attempt to monitor the infiltration process associated with pipeline leaks using the AHFO-OFDR technique, which is a reliable method for structural health monitoring of underground pipelines.

Laser welding simulation of large-scale assembly module of stainless steel side-wall

Due to the advantageous characteristics of laser welding technology, it is being increasingly used for constructing stainless steel rail vehicles. It can improve the appearance of a vehicle, enable designs with a relatively high degree of flatness, and ensure higher-quality connections between different parts of a vehicle. Moreover, it can improve the strength and stiffness of the components of the vehicle. In this study, a large-scale assembly module of a stainless steel side-wall was considered as the research object. The combined heat source model of a Gaussian heat source and a cylindrical volume heat source was used to obtain the heat source parameters of laser welding to match the experimental data. Based on the thermal cycle curve method (TCCM), the influence of the number of weld segments and mesh divisions of the local model on the efficiency and accuracy of laser welding simulations was investigated. Thereafter, the research results were applied to the welding simulation of the whole side-wall module. The shape of the molten pool obtained using the combined heat source was closer to that of the experiments (error < 10%), demonstrating the accuracy and effectiveness of the developed the heat source model for laser welding simulation. For local model laser welding using the TCCM, a coarse mesh was used, and the weld was divided into four segments, and highly accurate results were obtained. This calculation time was only 5.97% of that of a moving heat source in case of the thermo-elastic-plastic method (TEPM). Residual stress and welding deformation of the stainless steel side-wall module were calculated according to actual process parameters and the results of local model simulation. Residual stress was discontinuously distributed at the weld segments, and it only slightly influenced the overall stress distribution. The maximum residual stress (462.15 MPa) occurred at the weld of the large crossbeam. Welding eight small and two large crossbeams influenced the deformation change and the maximum deformation (1.26 mm) appeared in the middle position of the left side-wall. The findings of this study show that the TCCM has high calculation accuracy and is sufficiently economical for predicting laser welding of large structures.

Cold plate performance enhancement based on parametric modeling of multiple structures

Power electronic equipment to miniaturization, high integration direction while facing the problem of high heat flow density and uneven temperature distribution. The large temperature fluctuations and uneven temperature distribution in the operation of power electronic equipment will lead to thermal stress, and excessive thermal stress or uneven distribution will cause fatigue failure of the packaging material, resulting in reduced reliability, module failure, and reduced life of power electronic equipment. In this paper, we propose two kinds of liquid-cooled flow channel non-linear reinforced heat transfer homogeneous liquid-cooled plate, which is theoretically derived to achieve the design requirement of uniform temperature on the heating side wall surface. The thermal design of the cold plate is carried out using ANSYS Workbench, and the indicators of various structures of the cold plate are analyzed and compared in terms of their ability to dissipate heat and maintain temperature uniformity. Based on the original runner structure, the heat dissipation performance of the rod structure and fin structure was evaluated, and the form of the internal heat dissipation structure of the runner was determined. The results show that the integrated liquid cooling plate temperature uniformity and flow resistance of both factors, the fin column heat sink is significantly better than the cylindrical fin column heat sink in the case of the same thermal resistance, the fin column heat sink flow resistance is significantly lower than the cylindrical fin column heat sink.

Establishing zone of influence (ZOI) for cylindrical heat source in dry sand

ABSTRACT Safe, proper design and installation of several thermo-active structures necessitate establishing zone of extent of heat migration in soil mass. This zone is termed as ‘zone of influence’, ZOI, and its determination is imperative to avoid unwanted situations, which could be threat to the surrounding structures. This is where in-situ monitoring of the temperatures in the near- and far-field would be quite prudent, however would be an expensive exercise. Therefore, COMSOL Multiphysics® was employed to determine the ZOI. Nevertheless, the relative efficiency of these tools in yielding the ZOI remains a big question, and requires results from experiments to validate. Hence, an attempt was made in this study to establish the ZOI of cylindrical heat source, which replicates geothermal energy pile in dry sands, by adopting novel experimental methodology. ZOI has been established for cylindrical heat source experimentally and numerically. Furthermore, unique mathematical equation has been developed by using regression analysis.

Passive Cooling of PV Modules Using Heat Pipe Thermosiphon with Acetone: Experimental and Theoretical Study

The effect of heat pipe thermosiphon in reducing the operating temperature of a photovoltaic panel has been analyzed theoretically and experimentally in this paper. Copper heat pipe thermosiphon with acetone as a working fluid was used. The theoretical study involved a heat balance analysis of the panel with cylindrical heat pipe with surface contact with the panel bottom. The experimental study involved recording temperature variations, with and without a heat pipe, which had very good agreement with the theoretical results of 2.61%. Additionally, the optimum quantity of acetone was 50 mL, with a maximum reduction in panel temperature of 10 °C.

Multiple Phase Change Material-Based Heat Sink for Cooling of Electronics: A Combined Experimental and Numerical Study

Abstract This paper reports an investigation of the thermal performance of an energy storage heat sink incorporated with multiple phase change materials (PCMs). A six-cavity cylindrical heat sink heated at the base is chosen for the investigations with Docosane, n-Eicosane, and Tetracosane as candidate PCMs. The phase transition of PCMs has been visualized with a digital camera and three-dimensional numerical simulations. The results show that the latent heat exploitation process of PCMs in a heat sink with multiple PCMs is different from the single PCM heat sink, where the PCMs in all cavities melt distinctly rather at a time, thereby opening up windows for obtaining deeper insights that can lead to better performing heat sinks. A trained artificial neural network (ANN) with 78 representative heat sink configurations based on the arrangement of the PCMs in the cavities as input and charging and discharging times as output is used to swiftly drive the optimization engine. Finally, multi-objective optimization is performed using the artificial bee colony algorithm with simultaneous consideration of two conflicting objectives (i.e., maximizing charging cycle time and minimizing discharging cycle time) of the heat sink. From the optimization study, best performing nondominated Pareto optimal heat sink configurations are obtained and validated with the in-house experimental results. From the investigations, it is found that the heat sink configurations with multiple PCMs perform on par with the single PCMs in the charging process and show a superiority of up to 24% in discharging process over a heat sink with single PCMs in terms of time to reach set point temperature.

Constructal Optimizations of Liquid-Cooled Channels with Triangle or Square Sections in a Cylindrical Heating Body

Two new integrated models with heat source–heat sink are established, in which isothermal liquid cooling channels with triangle or square sections are, respectively, embedded in a cylindrical heating body with uniform heat production. Based on constructal theory, under the conditions of a fixed cylinder cross-sectional area and the proportion of channels, taking the dimensionless maximum temperature and the dimensionless entransy equivalent thermal resistance (EETR) as the optimization goals, the influences of distribution of liquid cooling channels on the heat dissipation capacity of integrated models are studied with the number and the center distance of liquid cooling channels as design variables, and the optimal constructs with different proportions of channels are obtained. The results show that when the proportion of channels, cross-sectional area and the number of liquid cooling channels are given, there is an optimal center distance to make the overall heat dissipation performance of the integrated model reach its best, but the optimal center distances for the two indicators are different. The dimensionless maximum temperature and the dimensionless EETR decrease when the proportion of channels increases, but the optimal dimensionless center distances are almost the same for different proportions of channels. The dimensionless maximum temperature with the triangular cross-section is lower than that with the square cross-section under the conditions of constant cross-sectional area and dimensionless center distance, which is the same as the case for the dimensionless EETR. The results can furnish the theoretical guidelines for the thermal design of cylindrical devices needing efficient cooling.

A Generic Digital Twin Application Framework for Emerging Trends in Industrial Process Heaters

Industrial process heaters have challenging future considering recent emission norms and efficient performance for cost optimization. It is therefore necessary to have real-time technical data and vigilant system to improve operations and elimination of abrupt failures. Though digital twin is highly suitable to address this requirement however its application knowledge for Process Heater is obsolete. Therefore, this paper objects to illustrate a generic digital twin methodology for industrial process heaters including key operational aspects which contain potential of optimization of performance and cost. The framework proposed in this study will integrate it to show its practical implications. This study is performed for typical vertical cylindrical process heaters; however, it is also applicable to other types of heaters. The ready to implement framework of digital twin will impact on saving of infrastructure development and limited dependability on commercial agencies while installation of digital twin. It will also address industrial challenges including reduction in emissions, fuel consumption, equipment downtime and unexpected failures. The framework will be path forward for future necessities like Artificial Intelligence, Machine Learning etc.

Вплив форми гравітаційної теплової труби з різьбовим випарником на її теплопередавальні характеристики

The modern development of electronics is associated with the problem of reducing the mass and size of the equipment while increasing its power. This leads to an increase in the temperature of both individual elements and the device as a whole, which contributes to a decrease in equipment reliability. This makes the development of inexpensive yet efficient cooling systems an urgent task. One of the ways to solve this problem is to use heat pipes of a new simplified design in cooling systems. This article compares the thermal characteristics of a cylindrical copper gravity heat pipe with a threaded evaporator before and after flattening. The working fluid used in the experiment was R141b. Experimental studies were conducted at two tilt angles relative to the horizontal under the conditions of forced convection cooling of the condensation zone. The influence of the change in the shape of the body from cylindrical to flat on the temperature in the heating zone of the heat pipe, thermal resistance, and heat transfer coefficients in the evaporation and condensation zones was shown in the range of heat power from 5 to 70 W. The choice of the heat pipe is justified based on the maximum thermal loads of electronic components and the orientation of the cooling system in space. Changing the shape of heat pipe from cylindrical to flat leads to a decrease in the maximum thermal power transmitted, but a flat heat pipe shape is more technologically feasible for use in cooling systems of electronic equipment.

Performances of a Cylindrical Heat Pipe Using Ferrofluid as the Working Liquid at Different Inclination Angles

Performances of a Cylindrical Heat Pipe Using Ferrofluid as the Working Liquid at Different Inclination Angles

Mathematical Modeling of a Thermal Converter with a Cylindrical Heat Pipeline and a Lumped Heat Source

Mathematical Modeling of a Thermal Converter with a Cylindrical Heat Pipeline and a Lumped Heat Source

Comparative Performance Analysis of Exhaust Air Heat Recovery Devices Based on Microchannel heat pipe

In response to the problem of low recovery efficiency of sensible heat recovery devices, this paper designs a microchannel heat pipe heat recovery device (MHPHRD) and compares its heat transfer performance during summer use through experiments and simulation calculations. The experimental results show that the microchannel heat pipe (MHP) has strong temperature uniformity, and the temperatures of the evaporation and condensation sections are basically the same. When the inlet temperature of fresh air changes between 32°C and 40°C, the recovery efficiency of the device varies between 67%-80%, and the linear relationship between the two is obvious. The established calculation model has high accuracy, with a maximum error of 0.7% between measured and simulated values. Simulation calculations show that the cooling capacity recovery efficiency of the MHPHRD is 4%-16% higher than that of the cylindrical heat pipe heat recovery device (CHPHRD), and 24%-30% higher than that of the plate heat recovery device (PHRD). The research in this article can provide reference for the practical application of the device.